Organic electroluminescence devices (hereinafter also referred to as “organic EL device”) comprising an organic compound are much expected to be useful as inexpensive, large-sized full color display devices of solid state emission type and many developments have been made thereon. An organic EL device is generally constructed from a light emitting layer and a pair of opposite electrodes sandwiching the light emitting layer. When an electric field is applied between the electrodes, electrons are injected from a cathode and holes are injected from an anode into the light emitting layer. The injected electrons recombine with the injected holes in the light emitting layer to form excited states. When the excited state returns to the ground state, the energy is released as light.
Many researches have been made on the applications of organic EL device to display, etc. because of its possibility of a wide selection of emission colors by using various emitting materials in a light emitting layer. Particularly, the research on the materials which emit three primary red, green, and blue colors has been made most actively, and the intensive research has been made to improve their properties.
As such materials for organic electroluminescence devices, Patent Literature 1 discloses a tertiary amine having two p-biphenylyl groups and one p-biphenylyl group having a N-carbazolyl substituent at the p- or m-position of the terminal phenyl group (compounds A-5 and A-20) and a tertiary amine having two p-biphenylyl groups and one m-biphenylyl group having a N-carbazolyl substituent at the p- or m-position of the terminal phenyl group (compounds A-21 and A-22).
Patent Literature 2 discloses a triphenylamine wherein each of three phenyl groups is p-substituted with a phenyl group optionally having a substituent at its o-position, m-position, or both. A specific example thereof is a triphenylamine wherein each of two or three phenyl groups is p-substituted with a m-substituted phenyl group, for example, a tertiary amine (1-21) wherein three phenyl groups of a triphenylamine are p-substituted with a m-phenylphenyl group, a m-(1-naphthyl)phenyl group, and a m-(N-carbazolyl)phenyl group; a tertiary amine (1-22) wherein three phenyl groups of a triphenylamine are p-substituted with an unsubstituted phenyl group, a m-(1-naphthyl)phenyl group, and a m-(N-carbazolyl)phenyl group; and a tertiary amine (1-23) wherein three phenyl groups of a triphenylamine are p-substituted with a m-(3-biphenylyl)phenyl group, a m-(1-naphthyl)phenyl group, a m-(N-carbazolyl)phenyl group.
Patent Literature 3 discloses a tertiary amine which essentially has a terphenylyl group and an aryl group having a N-carbazolyl substituent or a C-carbazolyl substituent. The tertiary amine has preferably two terphenylyl groups (paragraph [0045]). As the specific examples thereof, a tertiary amine having two p-terphenylyl groups and one p-(N-carbazolyl)phenyl group; a tertiary amine having two p-terphenylyl groups and one p-(N-carbazolyl)-3-biphenylyl group; and a tertiary amine having a p-terphenylyl group, a 3-(m-terphenylyl) group, and a p-(N-carbazolyl)-3-biphenylyl group are disclosed (paragraph [0059]).
Patent Literature 4 discloses a tertiary amine which has essentially one or two m-(N-carbazolyl)phenyl groups, for example, the tertiary amine A-4 having a p-terphenylyl group, a p-biphenylyl group, and a m-(N-carbazolyl)phenyl group.
Patent Literature 5 discloses a tertiary amine having a N-carbazolyl group, for example, the compounds 4 and 16, etc.